Subject: G7) Does an active June and July mean the rest of
the season will be busy too?Contributed by Stan Goldenberg (HRD)

Yes and No. The vast majority of Atlantic activity takes place
during August-September-October, the climatological peak months
of the hurricane season. The overall number of named storms
(hurricanes) occurring in June and July (JJ) correlates at an
insignificant r = +0.13 (+0.02) versus the whole season activity.
In fact, there is a slight negative relationship between early
season storms (hurricanes) versus late season - August through
November - r = -0.28 (-0.35). Thus, the overall early season
activity, be it very active or quite calm, has little bearing on
the season as a whole. These correlations are based on the years
1944-1994.

However, as shown in (Goldenberg 2000),
if one looks only at the June-July Atlantic tropical storms and
hurricanes occurring south of 22°N and east of 77°W (the
eastern portion of the Main Development Region [MDR] for Atlantic
hurricanes), there is a strong association with activity for the
remainder of the year. According to the data from 1944-1999,
total overall Atlantic activity for years that had a tropical
storm or hurricane form in this region during JJ have been at
least average and often times above average. So it could be said
that a JJ storm in this region is pretty much a "sufficient" (though
not "necessary") condition for a year to produce at least average
activity. (I.e., Not all years with average to above-average
total overall activity have had a JJ storm in that region, but
almost all years with that type of JJ storm produce average to
above-average activity.) The formation of a storm in this region
during June-July is taken into account when the August updates
for the
Bill Gray and
NOAA seasonal forecasts are issued.